This application is based on Japanese Patent Application Nos. 2000-42076, 2000-42077, 2000-42078, 2000-42079 filed Feb. 18, 2000 in Japan, and 2000-133895 filed May 2, 2000, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink-jet printing head which is capable of detecting ink therein, a substrate for an ink-jet printing head (hereinafter, simply referred to as a substrate) to be used in the ink-jet printing head, an ink-jet cartridge provided as a combination of the ink-jet printing head and an ink tank, an ink-jet printing apparatus which is capable of performing a printing movement using the printing head and/or the ink-jet printing cartridge, and a method for detecting ink in the printing head.
2. Description of the Prior Art
There are various kinds of printing apparatuses. For example, there are those having the functions of printing, copying, and transmitting, and also those provided as output devices for complex systems such as computers, word processors, and work station system. Each of these printing apparatuses is configured to print an image on a sheet of printing medium such as a sheet of paper or plastic thin plate (e.g., an overhead transparency film). Depending on their methods of printing, those printing apparatuses can be grouped into one of ink-jet, wire dot-matrix, thermal, heat-transfer, or laser beam type devices.
Among the groups of the printing apparatuses, the printing apparatus of the ink-jet type (the ink-jet printing apparatus) is one that performs a printing movement by ejecting ink onto a printing medium such as a sheet of printing paper, and allows the printing means to be as compact as possible with high speed printing of a fine detailed image. Furthermore, an image can be printed on a sheet of normal paper without previously processing a surface of such a sheet with specific chemicals or the like, so that the printing movement can be performed at low running expenses. In addition, the ink-jet printing apparatus is one of non-impact printing apparatuses that make images on the paper without striking it mechanically, so that it is capable of printing with a low noise. Furthermore, the ink-jet printing apparatus has additional advantages such as the ability of smoothly printing an image in multiple colors using several colored inks.
There are several procedures that may be performed by the ink-jet printing system. One of them is a bubble-jet printing system in which a heating element that provides ink in a nozzle with thermal energy to form a bubble in the ink and concurrently ejects ink from the nozzle by energy caused by the formation of the bubble. In this case, the thermal element provided as a printing element for causing the energy for ejecting ink from the ejecting port is prepared using semiconductor production processes well known to those of skill in the art. Therefore, the ink-jet printing head that utilizes the bubble-jet printing system may be constructed by the steps of forming printing elements on a substrate made of silicon and combining the substrate and a top plate together, where the top plate is made of a resin such as polysulfone or a glass material and has grooves to be formed as ink passages.
As the substrate is provided as a silicon substrate, various functional parts may be installed on the substrate in addition to the printing elements. The functional parts may be a driver for driving the printing elements, a thermal sensor to be used when the printing elements are regulated in response to temperature variations in the printing head, a control unit for adjusting the actuating status of the thermal sensor, and soon.
In Japanese Patent Application Laid-open No. 7-256883 (1995), by way of example, a substrate for the above ink-jet printing head is disclosed. The substrate disclosed in that document is configured as shown in FIG. 9.
In FIG. 9, a component substrate 100 is provided as a substrate of the printing head, on which a plurality of heating elements 101 is mounted as printing elements for providing ink with a thermal energy for the ejecting of ink. As shown in the figure, the heat elements 101 are arranged in parallel and connected to power transistors (driver elements) 102, respectively. The power transistor 102 is responsible for driving the corresponding heat element 101. Furthermore, a shift register 104, a latch circuit 103, and a plurality of AND gates 115 are mounted on the substrate 100. Image data can be serially transferred from the outside to the shift register 104 through a terminal 106 in synchronization with a serial clock signal entered through a terminal 105, storing one line of the image data in the shift register 104. The latch circuit 103 latches one line of the image data provided as a parallel output from the shift register 104 in synchronization with a latch clock signal (a latch signal) provided as an input from the outside to the latch circuit 103 through a terminal 107. The data is transmitted to each of the power transistors 102 in parallel. The AND gates 115 are connected to their respective power transistors 102. An output signal from the latch circuit 103 can be applied on the power transistor 102 in response to an enable signal from the outside. In FIG. 9, reference. numeral 108 denotes a drive pulse width (heat pulse) input terminal for input of a control signal from the outside of the printing head portion. The control signal controls the ON time of the power transistor 102 provided as the driving element. In this case, the control signal is for controlling the time of driving the heating element 101 by feeding a current through the heating element 101. Furthermore, reference numeral 109 denotes a terminal for an input of a driving source (5V) to logic circuits including the latch circuit 103 and the shift transistor 104. A ground terminal 110, terminals 112 for activating and monitoring the sensor 114, and so on are also mounted on the substrate 100. Accordingly, the terminals 105 to 112 formed on the substrate 100 are provided as input terminals for inputs of image data and various signals from the outside, respectively.
On the substrate 100, furthermore, there is mounted a sensor 114 such as a temperature sensor for measuring the temperature of the substrate 100 or a resistance sensor for measuring the resistance of each heating element 101. The printing head includes the substrate, on which the drivers, the temperature sensor, the drive control part, and so on are mounted, so as to contribute to make the device more reliable and small.
In the printing head as constructed above, an input image data as a serial signal is converted to a parallel signal by the shift resistor 104 and maintained by the latch circuit 103 in synchronization with the latch clock signal. In this state, a drive pulse signal for driving the heating element 101 (i.e., an enable signal for the AND gate 115) is sent to the input terminal 107 to switch the power transistor 102 on in response to the image data. Subsequently, the switched-on power transistor 102 feeds a current through the corresponding heating element 101 to generate a thermal energy from the heating element 101. The top plate (not shown) is fixed on the substrate 100 to form liquid passages (i.e., nozzles) for ejecting ink and a common liquid chamber that communicates with these liquid passages. The printing head is configured in this manner, so that ink stored in the ink tank (i.e., ink-reserving part) is supplied to each nozzle through the common liquid chamber, resulting in a stable supply of ink. Subsequently, as described above, the ink in the liquid passage (nozzle) is heated by thermal energy generated by driving the heating element to eject ink as a liquid droplet from an ejecting port formed on the tip of the nozzle.
One of the important points for performing printing movement to produce printed matter with stability is the stable existence of ink in the common liquid chamber and each nozzle of the printing head during the printing movement. If the amount of ink in the ink tank is decreased, or air is trapped in the inside of the nozzle from the tip thereof, or a bubble generated in the common liquid chamber moves to the inside of the nozzle, or any other undesired event is caused, an image of poor quality is generated because the printing head has difficulty ejecting ink. For instance, if one of a plurality of nozzles in the printing head becomes difficult to ejecting ink with stability, such a specific nozzle is defined as a faulty nozzle. In this case, the faulty nozzle misses its image formation, so that a stripe portion is formed on a portion where an image formation is missed during the process of printing the image on the printing medium. If the amount of ink in the common liquid chamber is decreased, there may be cases where ink is supplied to only some of the nozzles. In this case, just as in the case described above, an image of poor quality is formed as a result of the faulty nozzle.
Conventionally, for detecting a partial ejecting failure of the printing head caused by its failed nozzle, several methods have been proposed for the purpose of detecting the condition of ink in the inside of the common liquid chamber or nozzle, especially for detecting the presence or absence of the ink.
Japanese Patent Application Laid-open No. 58-118267 (1983) proposes the method for detecting the presence or absence of ink in each of nozzles arranged in the ink jet printing head. According to this method, an additional element is arranged in the inside of the nozzle in addition to the printing element. The additional element changes its resistance in response to variations in temperature. If ink in the ink tank is used up, the rate of increasing the temperature around the nozzle increases as the heating element (i.e., the printing element) produces heat. Such variations in the temperature are detected by the temperature-sensing element to determine the presence or absence of ink.
Regarding the structure of the printing head disclosed in Japanese Patent Application Laid-open No. 58-118267 (1983) described above, there is a need to provide each nozzle with a sensor or an element capable of detecting temperature. In addition, a driving element for actuating the sensor or the element should be also arranged in the nozzle or on the substrate used for fabricating the printing head. Thus, the printing head design disclosed in the above document can be efficiently applied to a printing head having large-sized nozzles arranged in comparatively less density.
In recent years, however, there is the growing need for performing a high-speed printing and forming an image with extraordinary definition. Thus, several attempts have been made year after year to meet the requirements. These attempts include an increase in the number of nozzles to be arranged in the ink-jet printing head and an arrangement of nozzles in high density to provide a high printing density.
Attempts have been made to arrange nozzles much more densely on the substrate of the ink-jet printing head. However, it becomes much more difficult to place a temperature-sensing element or sensor that corresponds to each of printing elements on the inside of a nozzle or an area adjacent thereto and also to place a driving element for actuating such an element or sensor. Likewise, the number of nozzles to be formed on the substrate is increased as the number of temperature-sensing elements or the like is increased. Therefore, it leads to a large-sized chip of the substrate for ink-jet printing head; a multiple layered structure of wiring layers for electrically connecting sensor elements, their related circuits, and so on; resulting in an intricate arrangement of components on the substrate and a high cost of chip manufacture.
In Japanese Patent Application Laid-open No. 58-118267 (1983), furthermore, no description is provided regarding the configuration of a terminal for electrically connecting the temperature-sensing element to the outside of the printing head. If terminals for their respective temperature-sensing elements are mounted on the substrate, the total number of various terminals required for the printing head can be increased. For establishing the electrical connection between the printing head and the printing apparatus, furthermore, flexible printed wiring or the like can be increased. In the printing apparatus, furthermore, the number of elements for individually controlling signals passing through the wiring can be increased. Therefore, it results in upsizing of various parts of the printing apparatus and leads to higher costs.
As described above, Japanese Patent Application Laid-open No. 58-118267 (1983) discloses the method for detecting the variations in temperature of the printing head. For that, such a method restricts a system of image formation to an ink-jet printing system in which a heating element that generates a thermal energy is used as a printing element.
A first object of the present invention is to provide a substrate for an ink-jet printing head, an ink-jet printing head, an ink-jet printing cartridge, and an ink-jet printing apparatus, which comprise means capable of detecting ink in the printing head by its considerably simple design and applicable to a wide variety of printing systems
A second object of the present invention is to provide a substrate for an ink-jet printing head, an ink-jet printing head, an inkjet printing cartridge, and an ink-jet printing apparatus, which comprise means capable of detecting ink in the printing head by its considerably simple design in a stable manner for the long term and applicable to a wide variety of printing systems.
A third object of the present invention is to provide a substrate for an ink-jet printing head, an ink-jet printing head, an inkjet printing cartridge, and an ink-jet printing apparatus, which comprise means capable of detecting the amount of ink in a nozzle, especially detecting the presence or absence of ink for every nozzle with a high degree of precision and with considerable simplicity of design.
A fourth object of the present invention is to provide an ink-jet printing apparatus and a method for detecting ink in an ink-jet printing head, which are applicable to various printing systems and capable of detecting ink in the ink-jet printing head with a high degree of precision and with a simplified design.
In a first aspect of the present invention, there is provided a substrate for an inkjet printing head to be provided as one of components that make up an ink-jet printing head that performs a printing movement by ejecting ink from an ejecting port, comprising:
a printing element for supplying energy for ejecting ink from the ejecting port;
a driving element for driving the printing element; and
a detection electrode provided at a position remote from the printing element communicating with a voltage monitor for detecting a voltage change between the printing element and the driving element via conductive ink on the substrate for the printing head, where the voltage change occurs in response to the driving of the printing element.
In a second aspect of the present invention, there is provided an ink-jet printing head, comprising:
the substrate for an ink-jet printing head of the first aspect, and
a top plate that forms nozzles corresponding to a predetermined number of printing elements when the substrate for the printing head is connected to the top plate.
In a third aspect of the present invention, there is provided an ink-jet cartridge comprising:
the ink-jet printing head of the second aspect; and
an ink tank that stores ink to be supplied to the ink-jet printing head and is connectable with the ink-jet printing head.
In a fourth aspect of the present invention, there is provided an ink-jet printing apparatus comprising:
a means on which one of an ink-jet printing head of second aspect and an ink-jet cartridge of third aspect is mountable to perform a printing movement on a printing medium.
In a fifth aspect of the present invention, there is provided a substrate for an ink-jet printing head to be provided as one of components that make up an ink-jet printing head that performs a printing movement by ejecting ink from an ejecting port, comprising:
a printing element for supplying energy for ejecting ink from the ejecting port;
a driving element for driving the printing element;
a detection electrode provided at a position remote from the printing element, communicating with a voltage monitor, for detecting a voltage change between the printing element and the driving element via conductive ink on the substrate for the printing head, where the voltage change occurs in response to the driving of the printing element; and
a protective film that covers a surface of the detection electrode.
In a sixth aspect of the present invention, there is provided an ink-jet printing head comprising:
a substrate for an ink-jet printing head of fifth aspect; and
a top plate which is bonded to the substrate for the printing head to form nozzles, where each nozzle corresponds to a predetermined number of the printing elements.
In a seventh aspect of the present invention, there is provided an ink-jet cartridge comprising:
the ink-jet printing head of the sixth aspect; and
an ink tank that stores ink to be supplied to the ink-jet printing head and is connectable with the ink-jet printing head.
In an eighth aspect of the present invention, there is provided an inkjet printing apparatus comprising:
a means on which one of the ink-jet printing head of the sixth aspect and the ink-jet cartridge of the seventh aspect is mountable to perform printing on a printing medium.
In a ninth aspect of the present invention, there is provided a substrate for an ink-jet printing head to be provided as one of components that make up an ink-jet printing head that performs a printing movement by ejecting ink from an ejecting port, comprising:
a printing element for supplying energy for ejecting ink from the ejecting port;
a driving element for driving the printing element;
a detection electrode which is placed a predetermined distance from both the printing element and the driving element via an insulating film; and
a reference element group which is different from a detection element group comprising the printing element, the driving element, and the detection electrode, where the reference element group has the same relationship as that of the printing element, the driving element, and the detection electrode.
In a tenth aspect of the present invention, there is provided an ink-jet printing head having a plurality of nozzles for ejecting ink, comprising:
a printing element installed in each of the nozzles for generating energy for ejecting ink;
a driving element for driving the printing element;
a detection means for detecting a change in voltage occurring at the printing element and/or the driving element at the time of driving the printing element by the driving element;
a reference element group which is provided as another element group which is different from a detection element group comprising the printing element and the driving element, where the reference element group has the same relationship as that of the printing element and the driving element; and
a detecting means that constitutes a reference unit together with the reference element group, wherein
a detecting means of the reference unit detects a voltage change that occurs in the reference element group by driving of the reference element group at the time of driving the reference element group in the same way as that of the detection element group, where the voltage change that occurs in the reference element group is considered as a voltage change that occurs when ink is in a predetermined state.
In an eleventh aspect of the present invention, there is provided an ink-jet cartridge constructed as a combination of an inkjet printing head having a plurality of nozzles for ejecting ink and an ink tank capable of storing ink to be supplied to the ink-jet printing head, comprising:
a printing element installed in each of the nozzles for generating an energy to eject ink;
a driving element for driving the printing element;
a detection means for detecting a change in voltage occurring at the printing element and/or the driving element at the time of driving the printing element by the driving element;
a reference element group which is provided as another element group which is different from a detection element group comprising the printing element and the driving element, where the reference element group has the same relationship as that of the printing element and the driving element; and
a detecting means that constitutes a reference unit together with the reference element group, wherein
a detecting means of the reference unit detects a voltage change occurring in the reference element group at the time of driving the reference element group by the same way as that of the detection element group, where the voltage change occurring in the reference element group is considered as a voltage change that occurs when ink is in a predetermined state.
In a twelfth aspect of the present invention, there is provided an ink-jet printing apparatus that uses an ink-jet printing head having a plurality of nozzles for ejecting ink and performs a printing movement on a printing medium by ejecting ink from the nozzles, comprising:
an inkjet printing head of tenth aspect; and
a means for detecting the presence or absence of ink in the nozzle on the basis of a comparison between a detection signal from the detecting means of the detection element group and a detection signal from the detecting means of the reference unit.
In a thirteenth aspect of the present invention, there is provided an ink-jet printing apparatus that uses an ink-jet printing head having a plurality of nozzles for ejecting ink and performs a printing movement on a printing medium by ejecting ink from the nozzles, comprising:
an ink-jet printing head of eleventh aspect; and
a means for detecting the presence or absence of ink in the nozzle on the basis of a comparison between a detection signal from a detecting means of the detection element group and a detection signal from a detecting means of the reference unit.
In a fourteenth aspect of the present invention, there is provided a substrate for an ink-jet printing head to be provided as one of components that make up an ink-jet printing head that performs a printing movement by ejecting ink from ejecting ports, comprising:
an energy-generating element for supplying an energy to be used for ejecting ink;
a driving element for driving the energy-generating element;
an insulating protective film which is formed to cover at least one selected from the energy-generating element, the driving element, and a wiring between the energy-generating element and the driving element;
a signal source connected to the energy-generating element and placed on a position covered by the protective film; and
a detection electrode capable of detecting a potential change between the signal source and the driving element to be generated in response to the driving of the energy-generating element via ink on the substrate for the printing head.
In a fifteenth aspect of the present invention, there is provided an ink-jet printing head comprising:
a substrate for an ink-jet printing head of fourteenth aspect.
In a sixteenth aspect of the present invention, there is provided an ink-jet cartridge comprising:
an ink-jet printing head of fifteenth aspect; and
an ink tank that stores ink to be supplied to the ink-jet printing head and is able to make a connection to the ink-jet printing head.
In a seventeenth aspect of the present invention, there is provided an ink-jet printing apparatus comprising:
a means on which an inkjet printing head of fifteenth aspect is mountable to perform a printing movement on a printing medium.
In an eighteenth aspect of the present invention, there is provided an ink-jet printing apparatus comprising:
a means on which an ink-jet printing cartridge of sixteenth aspect is mountable to perform a printing movement on a printing medium.
In a nineteenth aspect of the present invention, there is provided an ink-detecting method for detecting ink in an ink-jet printing head which is capable of ejecting ink from a plurality of ejecting ports, wherein
a substrate for an inkjet printing head mounted on the ink-jet printing head, comprises:
an insulating protective film which is formed to cover at least one selected from the energy-generating element, the driving element, and a wiring between the energy generating element and the driving element;
a signal source connected to the energy-generating element and placed on a position covered by the protective film; and
a detection electrode capable of detecting a potential change between the signal source and the driving element to be generated in response to the actuation of the energy-generating element via ink on the substrate for the printing head, wherein
a signal in response to the driving of the energy-generating element is generated from the signal source, and ink in the printing head is detected in response to a voltage change between the signal source and the driving element, which is detected by the detection electrode.
In a twentieth aspect of the present invention, there is provided an ink-jet printing apparatus for printing an image on a printing medium using an ink-jet printing head which is capable of ejecting ink by an energy generated by a printing element, comprising:
a detecting means that allows a detection of ink in the printing head in response to a detection signal obtained at the time of detecting a drive signal of the printing element via ink in the printing head; and
a supplying means for supplying an ink-ejecting drive signal with a level insufficient to ejecting ink to the printing element.
In a twenty-first aspect of the present invention, there is provided an ink-detecting method for detecting ink in an ink-jet printing head which is capable of ejecting ink by an energy to be generated from the printing element, in an ink-jet printing apparatus for printing an image on a printing medium using such a printing head, comprising the steps of:
supplying an ink-detection drive signal to the printing element, where a level of the ink-detection drive signal is insufficient to eject ink; and
detecting ink remaining in the printing head on the basis of a detection signal when the ink-detection drive signal is detected via ink in the printing head.
According to the present invention, changes in voltage between the printing element and the driving element occur when the printing element is driven or suspended. Such changes in voltage are transmitted with alternating current through ink. An insulation material such as a protective film provides electrical isolation between ink and a voltage-generating area where voltage is generated between the printing element and the driving element.
Concretely, the detection electrode detects changes in voltage to be transmitted with alternating current through ink. The presence or absence of ink is detected through voltage changes as the amount of remaining ink varies. Therefore, for example, a transmission part of the voltage-generating area to be transmitted with alternating current is provided so that it is electrically separated from each printing element. Then, the presence or absence of ink can be detected for every nozzle through the use of changes in electrical resistance.
According to the present invention, a signal source of ink-detecting signals is a printing element itself. As in the case of the conventional example described above, heat of the printing element is not utilized. Therefore, the detection electrode may be shared with all of the printing elements on the substrate. If the printing element is a heating element, furthermore, the detection electrode can be formed on the heating element concurrently with the formation of a anti-cavitation film thereon.
In the present invention, the detection of ink does not utilize heat, so that it can be applied to various printing systems using various printing elements because of its features in which changes in voltage occur when the printing element is driven.
In the present invention, a protective film such as an insulating film covers the surface of the detection electrode, so that the detection electrode can be prevented from incurring any physical or other change by making contact with ink. If the detection electrode is soaked in ink, the erosive action, adhesion, or the like of any constituent of the ink may be incurred depending on the type of the ink. Therefore, there is a fear of causing any change in a detection signal by such contact. The present invention permits the protection of the detection electrode without regard to the type of ink by coating the detection electrode with the protective film such as the insulating film, so that ink can be detected with a high degree of precision and a high accuracy of ink detection can be maintained for a long time.
According to the present invention, furthermore, if the printing element in the nozzle is driven by the driving element, the presence of ink can be detected as follows. That is, for example, changes in voltage occur in ink on the protective film provided as an insulating film on the top of the printing element and so on. Such changes in voltage can be detected by a detecting means such as an electrode through ink. In this configuration, a cluster of reference elements or a reference unit is mounted on a predetermined place in the same fashion as the above detecting means. Then, a difference between a signal detected by the above detecting means and a signal detected by the cluster of reference elements or the reference unit is calculated. The resulting difference allows a judgement of whether ink is present or absent at the predetermined portion where the detection has been performed. Accordingly, the impact of noise upon the above detection can be removed by the above difference.
As a result, it becomes possible to detect the amount of ink in the nozzle, especially the presence or absence of ink in each of the nozzles with precision by the simplified configuration of the ink-jet printing head.
According to the present invention, furthermore, a potential difference between the signal source and the driving element arises according to the activation of the energy-generating element. The changes in potential are detected by the detection electrode through ink in the printing head, so that the condition of supplying ink can be detected with respect to the temperature of the inside of a nozzle. Comparing with that of the prior art, there is no need to fabricate temperature sensors or the like. Therefore, the ink-jet printing head can be constructed more compactly and more cheaply. According to the present invention, furthermore, a protective film is formed on the signal source, which is different from the energy-generating element, so that a signal to be detected by the detection electrode can be amplified to detect the signal with a high degree of precision.
If the wiring for electrically connecting between the energy-generating element and the driving element is formed on a layer below the signal source formed on the substrate, the printing head can be protected from the impact of noise generated from the wiring or the like, resulting in an improvement in S/N.
Furthermore, all compositions except the energy generating element and the driving element may be covered with an organic film. In this case, the detection signal may be protected from noise consisting of signals from various logic circuits, wiring, and so on, resulting in detection with an even higher degree of precision.
According to the present invention, still furthermore, the ink-detection driving signal of an intensity insufficient to eject ink can be supplied to the printing element of the printing head. In this case, the ink-detection driving signal is detected through ink in the printing head to generate a detection signal. Then, the presence or absence of ink can be determined in response to the detection signal. Therefore, ink in the printing head can be detected with a high degree of precision by a considerably simple structure while the ink is kept under a stable environmental condition.